Get a 1960's car, that badly needs a tune-up. Run it right outside the window while giving your lecture. Make sure the breeze is carrying the exhuast into the room. If people get up and move, that should be a perfect example.

Biking is only better if:
You don't have to go too far and don't have too strict a time frame to get there
You don't have to carry a lot of stuff
You don't have a tendency to buy watermelon and other large items
You aren't one of these pantyhose, make-up and poofy hair ladies (or at least you don't have to be that way all the time)
You aren't super sweaty or don't live in a super hot place
You aren't terrified of traffic
You don't have to pick up the kids on the way home from work or drop them off on the way there
Your bike doesn't cause you pain

I could go on, but yeah, it's way better to ride a bike than drive, and I don't even live someplace flat.

Seriously, the reasons are parking and traffic, with fun coming in third. The big benefit to others is that you don't make parking and traffic worse for them. That's actually a big selling point -- in polls, the biggest reason people support mass transit is that they envision others using it, so they themselves can drive more easily. The way to get people behind cyclist accomodation is to convince them it will make driving easier by reducing traffic and demand for parking. Most people don't think about the big picture and only think of bikes as more competition for scarce space on the road.

You might also want to add that practically every day there's additional evidence that getting a little moderate exercise every day greatly reduces your risk of a wide variety of diseases. The most recent was last week where a study indicated that it reduced visceral fat (fat within/between organs, as opposed to externally carried fat) which is a risk factor for many forms of cancer.

Bike commuting is a great way to get that exercise in. If you count the time you DON'T have to spend specifically exercising and not doing anything else, you can take a lot more time commuting and still come out even. Plus, commuting is way more fun than sitting in a room staring at a wall working on a machine; boring = probably won't stick with the exercise program.

1. save time by combining commute time and cardo improvement [exercise ] time.
2. save money as cost per mile is much lower than motor vehicle 60cents/mile. [AAA figures]
3. extend lifespan by five to ten years because have better cardio reserves.
4. save pride as your commute sculpts your body so it is more appealing.

Assumptions:
1. commute between 5 and 15 miles one way
2. don't regularly exercise other than gym
3. only works saving time and money for cyclocommuting without need to carry heavy loads or children
4. can either buy a new bike every 2-4 years, or go on overseas vacation with savings
5. able to physically ride a well adjusted bike without pain
6. able to change at work to appropriate attire